This application is based on and claims priority to Japanese Patent Application No. 2000-230968, filed Jul. 31, 2000, the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
The present application generally relates to an engine control arrangement for controlling a four-stroke watercraft, and more particularly relates to an engine management system that prevents engine stalling under rapid deceleration.
2. Description of the Related Art
Watercraft, including personal watercraft and jet boats, are often powered by an internal combustion engine having an output shaft arranged to drive a water propulsion device. Occasionally, rapid deceleration occurs at high watercraft speeds and, because watercraft do not have brakes, water resistance experienced along the sides of the hull are the primary source of deceleration.
Watercraft often operate within three modes of operation: displacement mode, transition mode and planing mode. During lower speeds, the hull displaces water to remain buoyant; this is the displacement mode. At a particular watercraft speed relative to the water, a portion of the hull rises up from the water and the watercraft begins planing across the water; this is the planing mode. Of course, the transition mode occurs between the displacement mode and the planing mode and involves the range of watercraft speeds that cause a transition between the planing and displacement modes.
Importantly, while the watercraft is planing (i.e., up on plane), the wetted surface area of the watercraft is decreased and the water resistance is substantially reduced. On the other hand, once the watercraft slows to a speed that brings the watercraft off plane (i.e., transition mode and/or displacement mode), the wetted surface area of the watercraft is significantly increased and the water resistance dramatically increases. Because the water resistance is higher in non-planing modes, the rate of deceleration of the watercraft is also higher in the non-planing modes than in the planing mode.
To move from the planing mode to either the transition mode or the displacement mode, a throttle valve often is rapidly closed to cause the watercraft to decelerate. In some instances, the throttle valve is allowed to close almost entirely under the biasing force of a return spring that acts against a throttle valve control cable and operation (i.e., finger or thumb paddle). This rapid closure of the throttle valve can induce a rapid deceleration state.
In a rapid deceleration state, the air supplied to the cylinder bores of the engine decreases at a much faster rate than the control system controlling a set of fuel injectors can react. Thus, the amount of fuel being injected into the cylinders is excessive with respect to the amount of air entering the cylinders; a rich air-fuel mixture results. An overly rich mixture tends to cause an engine to stall. In addition, because the speed of the water passing the propulsion device tends to affect engine speed, the move from planing mode can cause the engine speed to decrease even more rapidly once the watercraft moves out of the planing mode and into the displacement mode. Thus, the engine is susceptible to stalling during rapid deceleration.
An additional problem in watercraft is irregularity in engine idle speed caused by variances in the air/fuel ratio. The variances generally are caused by condensation of the fuel within the combustion chamber and/or the induction system. In particular, when the engine is operated below a certain temperature, the fuel in the air/fuel mixture tends to condense on the walls of the intake manifold, the intake port and the cylinder walls. Such condensation increases the air/fuel ratio, which adversely affects engine performance.
Accordingly, an engine control arrangement has been developed to better control engine speed during rapid deceleration in order to prevent stalling. In addition, the engine control arrangement can be configured to maintain the air/fuel mixture at a desired ratio by adding more fuel at lower temperatures to return the air/fuel ratio to a desired level.
Thus, one aspect of the present invention involves a method of controlling a marine engine associated with a watercraft. The method comprises sensing a rapid deceleration when the watercraft is in a planing mode, altering an engine operating parameter to increase the engine speed when the rapid deceleration occurs when the watercraft is in the planing mode, sensing when an engine speed has attained a stabilized engine speed lower than an engine speed associated with the planing mode and returning the engine operating parameter to normal after then engine speed has attained the stabilized engine speed.
Another aspect of the present invention involves a personal watercraft comprising a hull adapted for at least two modes of operation: a planing mode and a displacement mode. An engine is disposed within the hull. The engine comprises a cylinder defined by a cylinder wall. A piston is reciprocally mounted within the cylinder. A combustion chamber is at least partially defined by the piston. The piston is drivingly connected to a crankshaft. A crankshaft sensor is adapted to sense a speed of the crankshaft. An induction system supplies air to the combustion chamber. A throttle valve is disposed within the induction system. An induction sensor is adapted to sense an airflow into the combustion chamber. An ignition system comprises an igniter that is disposed within the combustion chamber to ignite an air-fuel charge within the combustion chamber. A controller is in electrical communication with the crankshaft sensor and the induction system. The controller is adapted to adjust an engine operating parameter if the watercraft is in the planing mode and if the engine undergoes a rapid decrease in engine speed. The engine operating parameter is adjusted such that a rate of engine speed decrease is slowed.